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LM3424-Q1: can I use LM3424 -Q1 IC for more than 5 A application

Part Number: LM3424-Q1
Other Parts Discussed in Thread: LM3424

can I use LM3424 -Q1 IC for more than 5 A application by changing its external passive components ? and if yes what are the possible changes required.

  • Shikha,

    LM3424 is a controller, so theoretically you can support any current in the converter by simply sizing the external switching components correctly.  What usually limits the maximum current capability is the size of the MosFET and specifically the total gate charge.  Very large FETs usually have high gate charge due to their low RDSon spec and this means it takes a more powerful gate driver to effectively turn the switch on and off.  In my experience 5A should be possible using the LM3424, but the edge rate may be a little slower than expected and cause somewhat higher switching losses.

    To design for 5A, you can use the datasheet design equations and size all components according to that guide.  Keep in mind that the DCR of your inductor will have a big impact at 5A output on your efficiency and your switching diode will also be critical.  The diode average current in a boost or buck-boost type topology is equal to the average LED current, so a typical Schottky diode (which you want to use if possible) will have around 500mV forward voltage which gives you 2.5W of loss on the diode!  Thermal design will definitely be the hardest part of this.

    In general, a 5A design is not trivial and will require some power electronics experience to design and build.

    -JP

  • thank you so much for this information but i want to use LM3424 as LED Driver in buck mode. My current requirement is 8A, is it possible?

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